I think that invigilators when collecting individual papers they will sure glance one empty space and will notify you, you could also make sure by asking an invigilator in your centre and ask them is it part of your duty to check that the candidate name is written. Dont worry too much as candy said once u signed it is known that you had attended the exam they will search for the paper no worries and plus (I think) if there was more than one un-named paper they could match the paper's handwriting with other papers you wrote, right?